Net DesignPart1

The flashcards below were created by user
Anonymous
on FreezingBlue Flashcards.

What are some of the way to address broadcast issue in traditional networks?

The two major problems with traditional networks have always

been availability and performance. These two problems are both impacted

by the amount of bandwidth available.

To improve network

performance it is important to reduce the number of broadcasts, because lot of

broadcast on a network causes downtime which can lead to failure. The more

broadcast domains you have the better and the smaller they are the better.

Introduce VLANS into your network, a network without VLAN means a big

broadcast. Sub netting is also another factor that helps increase performance

on a network.

What is a 20/80 Rule and explain diagram?

In today's networks, traffic patterns are moving toward the 20/80

model. In the 20/80 model, only 20 percent of traffic remains local to the workgroup

LAN, and 80 percent of the traffic leaves the local network.

What are the key requirements that placed pressure on the emerging campus designs or what are the recommendations by CISCO for campus design?

Fast Convergence: To adapt very quickly to changes in the network topology, for example if a subnet goes down we expect the router or routing protocol that is implemented in that network to trigger very quickly updates to this network. EIGRP and OSPF are example of protocols that help propagate updates for fast converge, they react quickly to changes. OSPF tends to be quicker for fast convergence than other

protocols

Deterministic Paths: To determine the desirability of a given path to a destination for certain applications or user groups. Spanning Tree is an example of a protocol that provides deterministic paths because the STP will go through a number of stages:

1 It will not disable links that are not fast, only links that are slower (in doing this your providing paths for communication that are

much faster)

Redundancy: To ensure the network is operational at all times. For example aggregation links this adds extra can be used in case one links fails the other link can be reactivated for continue use. HCRSP load balance is other example. Making sure

providing alternative routes so that the network is functional all the time

Scability:Able to handle the increased traffic demands. How do you increment scability? Down to many factors such as hardware,

software, logical design, physical designs. You need to think about the logical

design first, it doesn’t allow you to scale, in the physical phase you need to

provide IP addresses in order to scale

Centralised application: They are available to support most of all users on the

network. For a centralised application will be in the server farm

Multi-Protocol support: Able to support multiprotocol environments. To be able to support multimedia environment you need to consider the types of protocol you run on

your network

Multicasting: Able to support IP multicast traffic e.g IGRP

20/80 Rule: Focuses on the shift in traditional patterns

What is VLAN and why is it needed?

VLAN takes on switch or one particular network and breaks it down into multiple logical networks. With VLANS you get security boundaries and broadcast separation.

What are the 2 types of VLAN?

End to end VLANs: Each VLAN is distributed geographically throughout the network. Users are grouped into each VLAN regardless of the physical location, which theoretically easing network management. A user moves throughout a campus, the VLAN membership for that user remains the same. Switches are configured for VTP server or client mode.

Local VLANS: Create local VLNAs with physical boundaries in mind rather than job function of the users. Local VLANs exist between the access and distribution layers/Traffic from a local VLAN is routed at the distribution and core levels/Switches are configured in VTP transparent mode/ Spanning tree is used only to prevent inadvertent loops in the wiring closet/One to three VLANs per access layer switch recommended

What are some of the characteristics of OSPF?

OSPF supports only IP routing

OSPF routes have an administrative distance of 110

OSPF uses costs as its metric, which is computed based on the bandwidth of the link

OSPF uses the Dijkstra Shortest Path First algorithm to determine the shortest path.

OSPF is a classless protocol, and thus supports VLSMs

OSPF consists of areas and autonomous system

What are the 3 separate tables that OSPF process builds and maintains?

Neighbor Table: Contains a list of all neighboring routers

Topology Table: Contains a list of all possible routes to all know networks within an area

Routing Table: Contains the best route for each know network

OSPF understand DR and BDR election processes/ How do you determine the DR?

However, only segments that are broadcast and nonbroadcast multi-access networks (examples are Ethernet and Frame Relay) will perform DR and BDR elections. Point-to-point links, like a serial WAN for example, will not have a DR election process.

On a broadcast or nonbroadcast multi-access network, the router with the highest OSPF priority on a segment will become the DR for that segment. This priority is shown with the show ip ospf interface command.

The default priority for a router interface is one. If all routers have the

default priority set, the router with the highest Router ID (RID) will win.

The RID is determined by the highest IP address on any interface at the moment of OSPF startup. This can be overridden with a loopback (logical) interface. If you set a routers interface to a priority value of zero,

that router wont participate in the DR or BDR election on that interface. The state of the interface with priority zero will then be DROTHER.

Explain what the cost of the link involves for OSPF: bandwidth delay, latency?

The shortest path (Lowest cost) is used in building topology and for selecting the best route. Faster links (higher bandwidth) have the

lower cost. So the lower the cost the better the route

What are the OSPF Router Types?

Internal: Routers with all their interfaces within the same area

Backbone: Routers with at least one interface connected to area 0

ASBR (Autonomous

System Boundary Router): Routers that have at least one interface connected

to an external internetwork (another autonomous system)

Area Border Router: Routers with interfaces attached to multiple areas

-Implementation (Test network and if can be reached, Implementation in real time)

-Operate

(Maintaining network health through day to day operations, including maintaining high availability and reducing expenses)

-Optimize

(Monitor network, Monitor and optimize, Software such as LMS to monitor

network, VLANS for optimization, Quality of service e.g. VoIP) proactive management of

network to identify and resolve issues before they affect the organization. Reactive fault detection and correction (troubleshooting) is needed when proactive management cannot predict and mitigate failures

What is the role of STP and its various forms?

In large networks topology changes occur frequently, thus high availability is very

important and necessary by using multiple links between switches in a network,

if one links fails the other links takes over, this provides redundancy. But

there is a big issues, redundant links causes storm loops within the network

this leads to both network bandwidth and resources starvation because broadcast

frames occur all the time in switched networks.

To solve the problem with infinite loops or broadcast storms a standardized protocol was created called the Spanning Tree Protocol (STP). The Spanning Tree

Protocol is an algorithm responsible for identifying active redundant links in

the network and blocking one of these links, thus preventing possible network

loops. STP is enabled by default in the switches. All switches generate and

Discarding: This state is seen in both a stable active topology and during topology synchronization and changes. The discarding state prevents the forwarding of data frames, thus “breaking” the continuity of a Layer 2 loop.

Learning: This state is seen in both a stable active topology and during topology synchronization and changes. The learning state accepts data frames to populate the MAC table to limit flooding of unknown unicast frames.

Forwarding: This state is seen only in stable active topologies. The forwarding switch portsdetermine the topology. Following a topology change, or during synchronization, theforwarding of data frames occurs only after a proposal and agreement process.